Currently manhole covers on railway pressure vessels are large, heavy steel plate circular covers which are bolted down with six to eight large eye bolts. The eye bolts that are used are a source of maintenance in that the bolts often break, the threads wearing, the nuts seize. In addition the installation and removal of the cover with the eye bolts is labour intensive, requiring a substantial amount of time in order to open and close the existing manhole covers.
Furthermore, the eye bolts securing the man whole cover are normally standing straight up with the threads exposed to the impact from tools, loading equipment and possible contact with the ground and other obstacles in the event of derailment of the rail car should the vessel overturn. Leaking of the pressure vessel can occur when an eye bolt is damaged or missing or the cover is incorrectly tightened or when the cover is permanently deformed from over tightening.
All of the above deficiencies in the existing manhole cover designs are the leading cause of commodity leaks in the north American rail car fleet.
Therefore, there is a need for a new and improved manhole cover locking system which overcomes the deficiencies of the current manhole cover designs and in particularly eliminates the need for six to eight large eye bolts which are positioned vertically upward from the cover.